Switchgrass is one of several crops poised to become a feedstock for the production of “cellulosic biofuels,” fuels derived from grasses, wood or the nonfood portion of plants. Though touted for being a clean energy alternative to both fossil fuels and corn ethanol, cellulosic biofuel comes with its share of complexities. Many of its environmental benefit depends, for starters, on how its crops are grown.

“We’ve established that the climate benefit of cellulosic biofuels is much greater and much more robust than people originally thought,” said Phil Robertson, University Distinguished Professor of Ecosystem Science at MSU and coauthor. “But what we’re also seeing is that much of that climate benefit is dependent. It’s dependent on factors such as land use history and – as we’re seeing with these results – it’s dependent on nitrogen fertilizer use.”

Led by former MSU graduate student Leilei Ruan and published this week in Environmental Research Letters, the study reports nitrous oxide emissions from switchgrass grown at MSU’s Kellogg Biological Station when fertilized at eight different levels.

“What we discovered is that there’s not a one-to-one relation between adding fertilizer and producing nitrous oxide,” Ruan said. “It’s not a linear relationship. After a certain amount of fertilizer is added, there is, proportionately, much more nitrous oxide produced than what you might expect.”